1. Field of the Invention
The invention relates to an electronic switch, preferably operating with zero contact, with an externally influenceable sensor stage, with an electronic load switch controllable by the sensor stage, and an integrated circuit (IC) provided between the sensor stage and the controlled input of the load switch. The integrated circuit comprising an evaluation stage for the sensor signal, a switchable inverter stage with switch input, and two driver stages operating in push-pull, with the output of the first driver stage controlling the load switch and the output of the second driver stage, in the "antivalent" mode, controlling another electronic switch.
2. Description of the Prior Art
Electronic switches of the type described above have replaced contact-encumbered, electrically or mechanically actuated switches in electrical measuring, control, or regulating circuits. This is especially true of electronic switches which respond with zero contact to a trigger, such as proximity switches. In proximity switches, in the presence of a trigger, the electrical properties of a sensor change, which sensor can be a dampable oscillator, a light barrier as an example of optical sensors, or, as another example, a gas detector. The electrical signals emitted by the sensor stage, usually preamplified, are fed to an evaluation stage whose digital output signal clearly determines for the following circuit stages whether the sensor stage has responded to a trigger or not. Depending on this signal, a load circuit is opened or closed by the following circuit stages, usually a driver stage and a load switch connected to it.
To avoid the cost of constructing electronic switches of the type described both as openers and as closers and to keep them in stock, the evaluation stage is followed by an inverter stage in which the digital output signal of the evaluation stage can be inverted as needed by applying a switching voltage to the special switching input of the inverter stage. By applying this switching voltage, a proximity switch with opener characteristics can be made from a proximity switch with closer characteristics (or vice versa).
In the course of miniaturization of electrical switches of the type described above, the evaluation stage, the switchable inverter stage, and the two driver stages that operate in push-pull are combined in an IC to save space. The space requirements of ICs basically reflect the number of their terminals, hereinbelow called IC contacts. In the known switch, one IC contact is required for applying the switching voltage to the inverter stage.